These are some of the very best resources not just on Thanksgiving, but the settling of the American Colonies. The first three links provide text, activities, videos, etc. that will provide ample material for K-8, especially. The Crash Course video is more for older students.
"What really happened at the First Thanksgiving?
Become a history detective and find out!
In this fun, award-winning activity, kids take on the role of "history detectives" to investigate what really happened at the famous 1621 celebration. (Hint: It was a lot more than just a feast!) Along the way, they'll read a letter written by an eyewitness to the event, learn about Wampanoag traditions of giving thanks, and visit Pilgrim Mary Allerton's home. As a final activity, kids can design and print their own Thanksgiving exhibit panel."
This would be a wonderful way for students to make something beautiful out of all the dirt samples they collect at Thanksgiving. Hopefully I could get an art teacher to partner up with me and do some of the background learning of the Japanese tradition.